Which of the following weeds is a root parasite?

Correct option is A

The correct answer is (A) Striga

Explanation:
• Striga, commonly known as witchweed, is a genus of parasitic plants that attach to the roots of host plants, primarily cereals like sorghum, maize, and pearl millet.
• It is a semi-root parasite (hemi-parasite) because while it performs some photosynthesis, it relies on the host for water and minerals.
• The seeds of Striga can remain dormant in the soil for many years and only germinate when they detect chemical signals (strigolactones) released by the roots of a potential host.
• Once germinated, the Striga seedling produces a haustorium that penetrates the host's root system to suck out nutrients, often causing severe stunting and crop failure.
• It is a major constraint to food production in sub-Saharan Africa and parts of Asia.

Information Booster:
• Parasitic weeds are classified based on the part they attack: Total Stem Parasite (Cuscuta), Partial Stem Parasite (Loranthus), Total Root Parasite (Orobanche), and Partial Root Parasite (Striga).
• Management of Striga involves crop rotation with non-host crops, use of resistant varieties, and 'suicidal germination' using synthetic strigolactones.
• The name 'witchweed' comes from the fact that the weed often causes damage to the crop before it even emerges from the ground.

Additional Knowledge:
• Cuscuta (Option B): A total stem parasite, also known as Dodder, which lacks chlorophyll and appears as yellow/orange leafless vines.
• Loranthus (Option C): A partial stem parasite commonly found on fruit trees like mango and citrus.
• Arceuthobium (Option D): Known as Dwarf Mistletoe, it is a genus of parasitic plants that live on various members of the Pinaceae and Cupressaceae families (conifers).